The present invention relates to a system for communication between sensors in training devices and the electrodes of an AED or an AED-T for the purpose of determining electrode positioning and providing feedback to the user.
For years, the use of AEDs in the case of sudden cardiac death has been recognized as the only curative treatment. Defibrillation involves the discharge of an electric pulse with relatively high energy through electrodes connected to the patient""s chest. Several designs of electrodes exist, but generally they can be divided into two groups: xe2x80x9cPaddlesxe2x80x9d are electrodes that are held manually on the chest. Adhesive electrodes or xe2x80x9cPadsxe2x80x9d are electrodes that are attached to the chest by the use of a conducting adhesive.
The electrodes are used both to discharge the electrical shock, to measure the patient""s ECG, and to measure any impedance.
Defibrillation may, by its very nature, involve a risk for those who treat the patient, if they touch the patient or in any other way come into contact with the electrodes.
Traditionally, defibrillation has been carried out by highly trained personnel in hospitals. However, AEDs have become much easier to use over the last ten years, and thus have also come to be used outside of the hospitals, primarily by the ambulance services. There is also a clear tendency for defibrillators to be used by the laity before the ambulance reaches the patient.
This means that there is a great need for training the users of defibrillators. Such training systems are available, and mainly consist of a training manikin and an electronic simulator. The defibrillator patient cable is connected to contact points on the chest of the manikin, and the simulator simulates typical heart rhythms, in addition to handling and registering the electric shock. The manikin and/or AED may also contain a report producer, which registers and reports the treatment that is being carried out.
In such a training system, the connection of the electrode takes place through galvanic coupling between the manikin and the AED, normally without the use of defibrillation electrodes. The ECG signal that is generated by the simulator is transmitted to the AED through the electrode connections, and the electric shock being discharged from the AED is transmitted the other way, to the manikin. The connections on the manikin must then have a typical patient impedance of approximately 50 Ohm, which must be able to absorb the relatively high energy from the AED. Beyond this, there is no direct communication between the manikin and the AED.
This has several disadvantages: Visible contact points are used for connecting the AED. This means that there is no opportunity for practicing realistic placement of electrodes based on anatomical references, or for practicing the manipulation that is required for effective connection and placement of the electrodes.
When the AED is used, it will normally give off an energy pulse of between 200 Joules and 360 Joules. The disadvantage of this is that the electronics in the manikin must handle both high voltages and high outputs, which makes the solution both large and costly. A further disadvantage is the fact that students may be exposed to high voltages, something that constitutes a safety risk. The fact that the energy is drawn from the AED battery is another disadvantage, as more and more AEDs are equipped with expensive, non-rechargeable primary batteries based on lithium.
There are AED-Ts available that do not have the disadvantages of high voltage and expensive lithium batteries. These devices do not interact with the manikin, and will operate in the same manner whether the electrodes are connected to the manikin or not.
AEDs that can run their own training software are also available. In this mode, the AED will not use the high voltage system, instead it will simulate the discharge of electric shocks and the measurements of the electrical activity of the heart. These devices have no interaction with the manikin either, and will operate in the same manner whether the electrodes are connected to the manikin or not.
Thus, an AED/AED-T is not able to indicate whether the electrodes have been placed correctly and have sufficient contact. Also, the manikin can not automatically be set to generate a noticeable pulse upon receiving a simulated electric shock.
It is essential to patient treatment that the electrodes be placed in the correct position on the patient, so as to deliver sufficient energy to the heart muscle. This correct emplacement is dependent on the user having been trained correctly, e.g., by practicing on a manikin.
Training equipment with the possibility of positioning AED electrodes is known from U.S. Pat. No. 5,137,458. In this, use has been made of Hall-effect sensors arranged in groups, with a permanent magnet and a monitor attached to the manikin for determination of the electrode positions, and for providing feed-back regarding the correct/incorrect placement of the electrodes.
U.S. Pat. No. 5,662,690 and U.S. Pat. No. 5,611,815 describe an AED that maybe set manually to two modes: training or treatment. The option of automatic detection of the state of connection between the AED and the training equipment is not mentioned in these patents. U.S. Pat. No. 5,275,572 describes training electrodes that are glued to the skin on a manikin""s chest, and further connect ed to an ECG simulator via cables.
The present invention aims to avoid the above mentioned disadvantages.
Further, the present invention aims to provide non-galvanic communication between the AED/AED-T and the training equipment, e.g. through the skin on the chest of the manikin, as well as detection of electrode positioning on the chest.
The present invention also aims to enable an AED to automatically measure whether it is connected to training equipment or to a patient.